In photochemotherapy for the treatment of non-superficial tumors, the patient is treated with a photosensitizing drug and optical radiation. The drug, which is generally administered to the patient 2 to 3 days before exposure to optical radiation, is absorbed in both normal and abnormal tissues throughout the body. However, the photosensitizing drug is retained for longer periods of time in tumor tissue as compared to most normal healthy tissue. Thus, over time, tumor tissue retains a higher concentration of the drug than does normal tissue.
The drug that is retained in the tissue provides for increased optical radiation absorption at selected wavelengths. This is referred to as photosensitization. The absorption of a sufficient amount of optical radiation following tissue photosensitization can result in tissue death.
Successful photochemotherapy treatment is dependent on the delivery of a sufficient amount of optical radiation to the entire tumor volume. For this reason, interstitial fiber optic applicators are used to deliver optical radiation inside deep seated tumors. However, the delivery of an excessive amount of optical radiation to the area of the tumor can result in unwanted damage to nearby photosensitized non-targeted normal healthy tissue. Thus, it is important to deliver an optimum amount of optical radiation to the tumor area, while avoiding overexposure and excessive damage to nearby or adjacent healthy tissue.
For this purpose, interstitial fiber optic dosimeters are used to monitor the optical radiation dose at strategically located sites within the tumor or near the tumor boundaries.
Present day dosimeters have certain disadvantages related to the manner in which they measure either the fluency of the treatment optical radiation directly or the fluorescence that it produces in a detector material. In either case, the fluency signal must be integrated over time in order to obtain a measure of cumulative dose. Thus, present day dosimeters do not provide a direct measurement of the cumulative dose. Another disadvantage with present day dosimeters is that the intensity of the signal they produce for measurement purposes is so low that it is often difficult to measure or detect at all. Because the intensity of the optical radiation at the treatment site to be measured is not very strong, treatment time can be as long as tens of minutes to several hours. Consequently, there is considerable uncertainty in the integrated value which is conventionally used to determine the cumulative dose. For these reasons, the accuracy of present day photochemotherapy dosimeter devices is limited.
The present invention provides a new and improved device for the measurement of optical radiation dose during photochemotherapy for the treatment of non-superficial deep-seated tumors.